T1W5: Laser Cutting RGB Nightlights
Now Meeting in the Innovation Studio - Primary School Building Room 120!
This week we will start some projects using the laser cutter in the Lowell Innovation Studio.
Laser Cutter Introduction
A laser cutter machine moves a powerful spot of infrared light in precise positions and speed over a two-dimensional surface to cut and mark flat materials. The Dremel LC40 laser cutter at Lowell has 40 Watts of power and can cut wood, fabric, leather, and plastics up to about 1/4" thick over a 20" x 12" area.
There are three different options for laser cutting: vector cut, where the laser beam cuts all the way through the material along a straight or curved path; vector score, where the laser etches a line in the surface without cutting all the way through; and raster engraving, where the laser scans back and forth over a rectangular area and builds up a picture by turning the beam on and off as it scans.
We will be doing a raster engraving on a anodized aluminum card to create a name tag for your Chromebook case. The laser is not powerful enough to cut through the aluminum but can turn the black or colored dye embedded in the metal's surface white, leaving a permanent mark.
Vector Graphics Editor - Google Drawings
An image editor like Adobe Photoshop can be used to design images that are raster engraved by the laser cutter, but to design the shapes for cutting or scoring requires a vector graphics editor. A vector graphics editor preserves the mathematical shapes of the objects in your design rather than converting everything to the values of pixels in a two-dimensional image grid. This allows the shapes to be used to guide the laser beam, and also maintains the precise resolution of the shapes as the design is moved, enlarged, or rotated.
You can use the Google Drawings program to create the design for your nametag. You can draw shapes, add text in different fonts and sizes, and import images. When you are done you will export your design as a .PDF file, which can be uploaded to the laser cutter.
Drawing Your Name Plate
To create a new drawing, visit the link above or from Google Docs press "+ New" and select a doc of type "More->Google Drawings".
Drawings opens with a blank document. Choose File->Page Setup->Custom and enter the size of the nameplate - 3.375" wide by 2.125" high. Then View->Zoom->Zoom Out to make it a little smaller on your screen.
Draw rectangles, add text, many fonts, can import clip art but keep in mind that colors don't get printed and high contrast b/w images are best.
Images Need To Be Inverted
Everything black on your PDF file will be etched to white on the black anodized aluminum surface, so the drawing will be inverted from how it looks in your editor. This isn't a big deal for line art and text but images imported will look funny - need to invert the contrast to make them look normal. The inverse function in the laser cutter software will invert everything including the text and background, so to invert just the image use the Google Drawings function "Format Options->Recolor->Negative". You may also adjust the Brightness and Contrast under "Format Options->Adjustment" to maximize the contrast of your image.
Exporting to .PDF file
When you are happy with the design, export it to a .PDF file on your Chromebook by selecting File->Download->PDF Document (.PDF)
Engraving Your Nameplate
When you are finished with your design, let me know - it's easier if only one person at a time is working with the laser cutter.
The laser cutter software is accessed through its web server. Pull up the webpage at: http://192.168.0.143, it should look like this:
Open the access door and place a blank metal name plate on the bed, against the metal ruler at the bottom. Use a small piece of blue painter's tape to hold the bottom edge of your nameplate to the ruler so it doesn't move around during the engraving.
Under the Import menu button, select "Capture" to scan the laser bed with a camera. After a while you should see an image of the metal honeycomb bed with the name plate and ruler replace the white grid.
Under "IMPORT" select file and navigate to the .PDF file you exported from Google Drawings. Select "IMPORT ENGRAVE" to bring in the PDF file as an image to engrave on your nameplate.
Find the PDF artwork on the workspace and move it on top of the image of the name plate on the bed. Zoom in on the nameplate using the +/- buttons at the lower right and reposition the image with the right mouse button. Adjust the position of your image to center it on the plate, and adjust the size if necessary - leave a little margin between the edges of the image and the metal plate to allow for misalignment.
Click on your design object and under MATERIAL, select "Anodized Aluminum". In the ENGRAVE tab, click on the gear icon to show the numeric values and set the DEPTH slider to 20%. Speed should be 100% and resolution should be MEDIUM.
If your image is all black and white objects and/or fonts, you can use the middle BLACK/WHITE THRESHOLD. But if you have an image or color or shading in clipart, select the rightmost GRAYSCALE icon to generate a halftone pattern.
When satisfied with the alignment, click on the "RUN PERIMETER" button and watch the laser bed while the laser cutter moves the laser head around the outside of your artwork. Make sure the little red dot moves inside your metal name plate.
Click the "RUN PERIMETER" button again to stop tracing the boundry, and click the START button to send the file to the laser cutter. The laser cutter coolant pump should start up.
On the front panel display of the laser cutter, read and touch the three safety check boxes, and then press the physical button twice to start engraving.
Watch the laser cutter bed as the engraving takes place. The whole pattern should take five minutes or so to engrave. When done you can open the door and remove your finished name plate!